(8 marks)
2. Calculate the pH of a buffer prepared by mixing HA with NaA. The buffer contains HA at a
concentration of 0.25 mol L-¹ After 0.20g NaOH is added to 100mL of this buffer, the pH of the
resulting solution is 5.60. The acid-ionization constant of HA is 5.0x106.
(10 marks)

Answer:

Mass = 19.68 g

Explanation:

Given data:

Mass of product formed = ?

Mass of Sr  16.4 g

Solution:

Chemical equation:

2Sr + O₂      →    2SrO

Number of moles of Sr:

Number of moles = mass /molar mass

Number of moles = 16.4 g/ 87.62 g/mol

Number of moles = 0.19 mol

Now we will compare the moles of Sr with SrO.

                     Sr           :         SrO

                      2           :           2

                    0.19        :         0.19

Mass of Sr:

Mass = number of moles × molar mass

Mass = 0.19 mol × 103.62 g/mol

Mass = 19.68 g

Answer:

D.) State the question, form a hypothesis, conduct an experiment

Explanation:

https://www.colorincolorado.org/article/steps-scientific-process

Answer:

About 200 moles water

Explanation:

O2 is the limiting reactant, and it allows for 193.75 moles of water to be produced. Good luck on your assignment!

Answer:

0.149 moles

Explanation:

The problem is asking us to convert 9.49 grams of copper into moles. We can do that by using copper's molar mass:

Now we proceed to calculate the number of moles:

There are 0.149 moles of copper in the wire.

Answer:

11690J

Explanation:

Use formula Q = mL

where:

Q = Energy (J)

m = Mass (g)

L = Latent heat of fusion for water (J/g) = 344J/g

Therefore:

Q = 35.0 x 344

Q = 11690J

Answer = 0

Explanation:

The sum of the charges of atoms of elements in a neutral compound is zero

Hence the charge of iron in the compound is 0

The charge on the iron ion in the salt Fe₂O₃ is + 3 as the charge on overall compound is 0.

An ion is defined as an atom or a molecule which has a net electrical charge. There are 2 types of ions :1) cation 2) anion . The cation is the positively charged ion and anion is the negatively charged ion . As they are oppositely charged they attract each resulting in the formation of ionic bond.

Ions consisting of single atom are mono-atomic ions while which consists of two or more ions are called as poly-atomic ions . They are created by chemical interactions . They are very reactive in their gaseous state and rapidly react with oppositely charged ions resulting in neutral molecules.

The charge on the iron ion in the salt Fe₂O₃ is calculated as 2×x+3(-2)=0  thus x= +3.

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Answer: 20.9 billion years.

Explanation: To estimate the age of the rock, we can use the fact that the half-life of uranium-238 is 4.47 billion years. This means that half of the uranium-238 in the rock would have decayed into lead-206 after 4.47 billion years, and half of what remains would decay in the next 4.47 billion years, and so on.

If 20% of the uranium-238 in the rock has decayed into lead-206, then 80% of the original uranium-238 is still present in the rock. This means that the rock has gone through one half-life of uranium-238 decay, and we can estimate its age by using the graph on page 253.

According to the graph, the ratio of lead-206 to uranium-238 after one half-life is approximately 0.027. This means that the rock contains 0.027 times as much uranium-238 as it did originally, and the remaining 80% of the uranium-238 corresponds to 0.8 times the original amount.

Therefore, we can estimate the original amount of uranium-238 in the rock as follows:

Original amount of uranium-238 = (0.8) / 0.027 = 29.63 times the current amount

Next, we can use the fact that each half-life corresponds to a reduction in the amount of uranium-238 by a factor of 2, to estimate the number of half-lives that have passed since the rock formed:

Number of half-lives = log2(29.63) = 4.88

Finally, we can estimate the age of the rock as follows:

Age of the rock = (4.88) x (4.47 billion years per half-life) = 20.9 billion years

Therefore, we can estimate that the age of the rock is approximately 20.9 billion years.

Heat is added to ice at 0 °C. Explain why the temperature of the ice does not change. What does change?When heat is added to ice at 0°C, the temperature of the ice does not change. This happens because all the heat energy is used up in overcoming the intermolecular forces of attraction (hydrogen bonds) that exist between the water molecules in ice.

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Divide the volume of water with mass of salt and multiply with 100 you'll get the concentration percentage

answer is B, because solution A's percentage is 10%

brainliest plz

Answer:

The compound which doesn't contains ionic character is HC, H-atom and CL- atom shares 1 electron a to form covalent bond....

The removal of the azo dye can be achieved by the use of the adsorbents.

We know that a dye could be one of the contaminants that could be seen to be present in an effluent stream. It is always very important that we should be able to remove the wastes that are part of a stream as this is going to make sure that we do not have the effluent filled with a contaminant.

The contaminant that is found in the stream can be able to be passed into the aquatic ecosystem and then it could be passed along food chain and this is going to cause a much larger damage to people that are living in a locality.

We can be able to remove the azo dye by the use of the adsorbents that would be able to take up the dye and such save the environment.

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The mass percent of iron in the mixture is 29.43%.

What is mass percent?

Mass percent, also known as percent by mass, is a way of expressing the concentration of a solute in a solution, or the composition of a mixture, in terms of the mass of the solute or component relative to the total mass of the solution or mixture, multiplied by 100%.

To determine the mass percent of iron in the mixture, we need to use the formula:

mass percent = (mass of iron / total mass of mixture) x 100%

We are given that the mass of the iron is 1.213 g, and the total mass of the mixture is 4.123 g.

So, substituting these values into the formula:

mass percent = (1.213 g / 4.123 g) x 100%

mass percent = 29.43%

Therefore, the mass percent of iron in the mixture is 29.43%.

What is concentration of solution?

Concentration of a solution is the amount of solute dissolved in a given amount of solvent, and is usually expressed as a unit of measure per volume or mass of the solution. The most commonly used units of concentration include molarity, molality, mass percent, volume percent, and parts per million.

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Explanation:

a. 1 nm = 10Å

683nm=683×10Å

=6830 Å

b. 1 mi/h=0.44704

520 mi/h=520×0.44704

=232.4608

c. 1 g/cm3=62.427961 lb/ft3

0.714 g/cm3=0.714×62.427961 lb/ft3

=44.573564

d. 1°C =9/5 +32 =33.8°F

-164°C = -164×9/5+32 = -263.2°F

Marks as brainest one.

Using the concentration equation, m = CVMo where m is the mass of solute, C is the concentration (M), V is the volume of solution (L) and Mo is molar mass of the solute (g):

Given,

Molar mass of NaCl, M = 58.5g/mol

Volume of the solution, V= 100ml = 0.1L

Molarity, S= 1M

Mass of the solute,W=?

W=SMV

= 1×58.5×0.1

= 5.85g

There are 7 unpaired electrons in [Ni(NH\(_3\))\(_6\)]\(_3\)⁺. The elementary electric charge of the electron is a negative one, making it a subatomic particle.

The elementary electric charge of the electron is a negative one, making it a subatomic particle. Due to their lack of components or substructure, electrons, which are part for the lepton particle family's first generation, are typically regarded to be elementary particles.

The mass of an electron is roughly 1/1836 that of a proton. The electron has a half-integer inherent angular momentum (spin) that is described in terms of the shortened Planck constant,, among its quantum mechanical features.  There are 7 unpaired electrons in [Ni(NH\(_3\))\(_6\)]\(_3\)⁺.

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A neutralizing reaction takes place when the acid and base are let to interact. The concentration of HCl is 218.12 M.

Determine how much 0.100 M HCI solution is required to neutralize 25.0 mL of 0.350 M NaOH. (Response: 87.5 mL) In order to neutralize 124 mL of 0.250 M NaOH solution, determine the volume of 0.100 M HzSO4 solution required. An acid and base process known as neutralization produces only salt and water. The OH- from the base totally neutralizes the H+ from the acid in this reaction. Therefore, we can define a neutralization reaction as a reaction that creates water by removing the H+ and OH- from the reactant. Here is an example to help you.

HCl + NaOH = NaCl + H₂OOH⁻ + H⁺

mol of solution = molarity × Liter solution

mol HCL = 16.8 ml × 0.50 M

               = 8.4 mol HCl

Concentration of HCl = 8.4/0.0385

                                    = 218.12 M

From the foregoing, it is obvious that the reaction converted the OH- and H+ from the base into water.

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The helium tank has a pressure of 650 torr at 25 degree Celsius and when the temperature is tripled, the pressure will be approximately 1945.71 torr

To find the new pressure when the temperature is tripled, we can use the ideal gas law, which states that the pressure of a gas is directly proportional to its temperature when the volume and the number of particles remain constant. The ideal gas law is given by the equation:

PV = nRT

Where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature in Kelvin.

First, we need to convert the initial temperature of 25 degrees Celsius to Kelvin. Adding 273.15 to the Celsius temperature gives us 298.15 K.

Let's assume that the volume, number of moles, and the gas constant remain constant.

If the temperature is tripled, the new temperature would be 3 times the initial temperature, which is 3 * 298.15 K = 894.45 K.

Now, we can set up a proportion to find the new pressure:

P1 / T1 = P2 / T2

Solving for P2 (the new pressure), we get:

P2 = (P1 * T2) / T1

Plugging in the values, we have:

P2 = (650 torr * 894.45 K) / 298.15 K

Calculating this expression, we find:

P2 ≈ 1945.71 torr

Therefore, when the temperature is tripled, the pressure will be approximately 1945.71 torr.

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After the reaction is complete, no nitrogen and no hydrogen molecules remain, and 8.00 x 1014 molecules of NH3 are produced.

In the equation, nitrogen and hydrogen react at a high temperature, in the presence of a catalyst, to produce ammonia, according to the balanced chemical equation:N2(g)+3H2(g)⟶2NH3(g)The coefficients of each molecule suggest that one molecule of nitrogen reacts with three molecules of hydrogen to create two molecules of ammonia.

So, to determine how many molecules of ammonia are produced when four nitrogen and nine hydrogen molecules are present, we must first determine which of the two reactants is the limiting reactant.

To find the limiting reactant, the number of moles of each reactant present in the equation must be determined.

Calculations:
Nitrogen (N2) molecules = 4Hence, the number of moles of N2 = 4/6.02 x 1023 mol-1 = 6.64 x 10-24 mol
Hydrogen (H2) molecules = 9Hence, the number of moles of H2 = 9/6.02 x 1023 mol-1 = 1.50 x 10-23 mol

Now we have to calculate the number of moles of NH3 produced when the number of moles of nitrogen and hydrogen are known, i.e., mole ratio of N2 and H2 is 1:3.

The mole ratio of N2 to NH3 is 1:2; thus, for every 1 mole of N2 consumed, 2 moles of NH3 are produced.
The mole ratio of H2 to NH3 is 3:2; thus, for every 3 moles of H2 consumed, 2 moles of NH3 are produced.
From these mole ratios, it can be observed that the limiting reactant is nitrogen.

Calculation for NH3 production:
Nitrogen (N2) moles = 6.64 x 10-24 moles
The mole ratio of N2 to NH3 is 1:2; therefore, moles of NH3 produced is 2 × 6.64 × 10−24 = 1.33 × 10−23 moles.

Now, to determine how many molecules of NH3 are produced, we need to convert moles to molecules.
1 mole = 6.02 x 1023 molecules
Thus, 1.33 x 10-23 moles of NH3 = 8.00 x 1014 molecules of NH3 produced.

To find the amount of each reactant remaining after the reaction is complete, we must first determine how many moles of nitrogen are consumed, then how many moles of hydrogen are consumed, and then subtract these from the initial number of moles of each reactant.

The moles of nitrogen consumed = 4 moles × 1 mole/1 mole N2 × 2 mole NH3/1 mole N2 = 8 moles NH3
The moles of hydrogen consumed = 9 moles × 2 mole NH3/3 mole H2 × 2 mole NH3/1 mole N2 = 4 moles NH3
Thus, the moles of nitrogen remaining = 6.64 × 10−24 mol – 8 × 2/3 × 6.02 × 10^23 mol-1 = 5.06 × 10−24 mol
The moles of hydrogen remaining = 1.50 × 10−23 mol – 4 × 2/3 × 6.02 × 10^23 mol-1 = 8.77 × 10−24 mol

Finally, the number of molecules of each reactant remaining can be calculated as follows:
Number of N2 molecules remaining = 5.06 × 10−24 mol × 6.02 × 10^23 molecules/mol = 3.05 × 10−1 molecules ≈ 0 molecules
Number of H2 molecules remaining = 8.77 × 10−24 mol × 6.02 × 10^23 molecules/mol = 5.28 × 10−1 molecules ≈ 0 molecules.

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Precision relates to the consistency and reproducibility of measurements, while accuracy reflects how close measurements are to the true value.

Precision and accuracy are two important concepts in the context of errors in measurements. While they both pertain to the quality of data, they refer to different aspects.

Precision refers to the degree of consistency or reproducibility in a series of measurements. It reflects the scatter or spread of data points around the average value. If the measurements have low scatter and are tightly clustered, they are considered precise. On the other hand, if the measurements have a high scatter and are widely dispersed, they are considered imprecise.

Accuracy, on the other hand, refers to the closeness of measurements to the true or target value. It represents how well the measured values align with the actual value. Accuracy is achieved when measurements have a small systematic or constant error, which is the difference between the average measured value and the true value.

Errors in measurements can be classified into two types: random errors and systematic errors.

Random errors are associated with the inherent limitations of measurement instruments or fluctuations in the measurement process. They lead to imprecise data and affect the precision of measurements. Random errors can be reduced by repeating measurements and calculating the average to minimize the effect of individual errors.

Systematic errors, on the other hand, are caused by consistent biases or inaccuracies in the measurement process. They affect the accuracy of measurements and lead to a deviation from the true value. Systematic errors can arise from factors such as instrumental calibration issues, environmental conditions, or experimental techniques. These errors need to be identified and minimized to improve the accuracy of measurements.

In summary, precision refers to the degree of consistency or reproducibility of measurements, while accuracy refers to the closeness of measurements to the true value. Random errors affect precision, while systematic errors affect accuracy. To ensure high-quality measurements, both precision and accuracy need to be considered and appropriate techniques should be employed to minimize errors.

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dolphin and whales use echolocation

The concentration of the HNO₃ solution needed to neutralize the 27.60 mL of 1.00 M NaOH is 2.76 M

The balanced equtaion is given below:

HNO₃ + NaOH —> H₂O + NaNO₃

Now, we shall obtain the concentration of the HNO₃ solution needed for the neutralization reaction. This is shown below:

CaVa / CbVb = nA / nB

(Ca × 10) / (1 × 27.6) = 1

(Ca × 10) / 27.6 = 1

Cross multiply

Ca × 10 = 27.6

Divide both side by 10

Ca = 27.6 / 10

Ca = 2.76 M

Thus, the concentration of the HNO₃ solution needed is 2.76 M

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The boys could cover the end of the test tube with a balloon to capture the escaping gas. Therefore, the correct option is option C.

A chemical reaction is the chemical change from one set of chemical components into another. Chemical reactions are changes that solely affect the locations of electrons inside the formation as well as breakdown of chemical bonds that link atoms, and without any modification to the nuclei, and therefore are frequently represented using a chemical equation.

Nuclear chemistry is the branch of chemistry that studies the chemical interactions of unstable especially radioactive materials, which can result in both electronic plus nuclear alterations. The boys could cover the end of the test tube with a balloon to capture the escaping gas.

Therefore, the correct option is option C.

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Answer:

In the atmosphere carbon is found as carbon dioxide

Explanation:

The molar mass of MgCrO4 is approximately 140.30 g/mol.

To determine the molar mass of MgCrO4 (magnesium chromate), we need to calculate the sum of the atomic masses of each individual element in the compound.

The chemical formula MgCrO4 indicates that the compound consists of one magnesium atom (Mg), one chromium atom (Cr), and four oxygen atoms (O).

The atomic masses of the elements can be found on the periodic table:

Magnesium (Mg) has an atomic mass of approximately 24.31 g/mol.

Chromium (Cr) has an atomic mass of around 51.99 g/mol.

Oxygen (O) has an atomic mass of about 16.00 g/mol.

Now, we can calculate the molar mass of MgCrO4 by summing up the atomic masses of each element, considering the respective subscripts:

Molar mass = (Atomic mass of Mg) + (Atomic mass of Cr) + 4 × (Atomic mass of O)

Molar mass = (24.31 g/mol) + (51.99 g/mol) + 4 × (16.00 g/mol)

Molar mass = 24.31 g/mol + 51.99 g/mol + 64.00 g/mol

Molar mass ≈ 140.30 g/mol

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Answer:

85.9%

Explanation:

There are two reactions to take into consideration for this problem:

The first one is the reaction of limestone with HCl:

      1) CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O

While the second one is the titration of HCL with NaOH:

          2) HCl + NaOH → H₂O + NaCl

So first we calculate the number of HCl moles added:

A number of those 5.175x10⁻³ moles reacted with limestone while the remaining excess reacted with NaOH.

The number of NaOH moles used in the titration is:

We know from equation 2) that the moles of NaOH are equal to the moles of HCl in the titration process.

That means that the number of HCl moles that reacted with CaCO₃ in the limestone sample is:

Now we use that number of HCl in equation 1) to calculate the number of CaCO₃ moles, which we then convert to grams using its molecular weight:

Finally we calculate the CaCO₃ percentage in the sample:

Answer:

1) SO₄ ²⁻ : (+6)

  H₂S : (-2)

Explanation:

a) Sulfate reducers are widespread in muds and other sediments, water-logged soils, etc., environments that contain SO₄ ²⁻ and become anoxic as a result of microbial decomposition.

Sulfate (SO₄ ²⁻), the most oxidized form of sulfur (+6), is reduced by these

sulfate-reducing bacteria. The end product of sulfate reduction is hydrogen sulfide, H₂S, (oxidation number -2) an important natural product that participates in many biogeochemical processes. The H₂S they generate is responsible for the pungent smell (like that of rotten eggs) often encountered near coastal ecosystems. When sulfate-reducing bacteria grow, the H₂S formed from SO₄ ²⁻ reduction combines with the ferrous iron to form black, insoluble ferrous sulfide, which is not toxic. This is important for the conservation of the environment.

b) The net ionic equation under acidic conditions is:

              4 H₂ + SO₄²⁻ + H⁺ → HS⁻ + 4 H₂O

    Global reaction:  SO₄²⁻ + 2H⁺ → H₂S + O₂